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CIHM/ICMH 

Microfiche 

Series. 


CIHIVI/iCIVIH 
Collection  de 
m 


Canadian  Instituta  for  Hiatorical  Microraproduction*  /  Inatitut  Canadian  da  microraproductiona  hiatoriquaa 


Technical  and  Bibliographic  Notes/Notes  techniques  et  bibliographiques 


The  Institute  has  attempted  to  obtain  the  best 
original  copy  available  for  filming.  Features  of  this 
copy  which  may  be  bibliographically  unique, 
which  may  alter  any  of  the  images  in  the 
reproduction,  or  which  may  significantly  change 
the  usual  method  of  filming,  are  checked  below. 


D 


n 


n 


Coloured  covers/ 
Couverture  de  couleur 


I      I   Covers  damaged/ 


Couverture  endommagte 

Covers  restored  and/or  laminated/ 
Couverture  restaur^  et/ou  pellicuMe 

Cover  title  missing/ 

Le  titre  de  couverture  manque 


D 
[3 


I     I   Coloured  maps/ 


Cartes  gtographiques  en  couleur 

Coloured  ink  (i.e.  other  than  blue  or  black)/ 
Encre  de  couleur  (i.e.  autre  que  bleue  ou  noire) 


I     I   Coloured  plates  and/or  illustrations/ 


D 


Planches  et/ou  illustrations  en  couleur 

Bound  with  other  material/ 
RellA  avec  d'autres  documents 

Tight  binding  may  cause  shadows  or  distortion 
along  interior  margin/ 

La  reliure  serr^e  peut  causer  de  I'ombre  ou  de  la 
distortion  le  long  de  la  marge  intArieure 

Blank  leaves  added  during  restoration  may 
appear  within  the  text.  Whenever  possible,  these 
have  been  omitted  from  filming/ 
II  se  peut  que  certaines  pages  blanches  ajouties 
lors  d'une  restauration  apparaissent  dans  le  texte, 
mais,  lorsque  cela  itait  possible,  ces  pages  n'ont 
pas  AtA  filmAes. 

Additional  comments:/ 
Commentaires  supplAmentaires; 


L'Institut  a  microfilm^  le  meilleur  exemplaire 
qu'il  lui  a  AtA  possible  de  se  procurer.  Les  details 
de  cet  exemplaire  qui  sont  peut-Atre  uniques  du 
point  de  vue  bibliographique,  qui  peuvent  modifier 
une  image  reproduite,  ou  qui  peuvent  exiger  une 
modification  dans  la  mAthode  normale  de  filmage 
sont  indiqute  ci-dessous. 


I     I   Coloured  pages/ 


D 
D 


Pages  de  couleur 

Pages  damaged/ 
Pages  endommagtes 

Pages  restored  and/oi 

Pages  restaurtes  et/ou  pelliculAes 

Pages  discoloured,  stained  or  foxet 
Pages  dAcoiortes,  tachetAes  ou  piqutes 

Pages  detached/ 
Pages  dAtachtes 

Showthrough/ 
Transparence 

Quality  of  prir 

Qualit*  inAgale  de  I'impression 

Includes  supplementary  materii 
Comprend  du  materiel  suppMmentaire 


I — I  Pages  damaged/ 

I — I  Pages  restored  and/or  laminated/ 

r~n  Pages  discoloured,  stained  or  foxed/ 

I     I  Pages  detached/ 

I      I  Showthrough/ 

|~n  Quality  of  print  varies/ 

I      I  Includes  supplementary  material/ 


Only  edition  available/ 
Seule  Mition  disponible 

Pages  wholly  or  partially  obscured  by  errata 
slips,  tissues,  etc.,  have  been  refilmed  to 
ensure  the  best  possible  image/ 
-Les  pages  totalement  ou  partiellement 
obscurcies  par  un  feuillet  d'errata,  une  pelure, 
etc.,  ont  At*  filmAes  A  nouveau  de  fapon  A 
obtenir  la  meilleure  image  possible. 


This  item  is  filmed  at  the  reduction  ratio  checked  below/ 

Ce  document  est  filmA  au  taux  de  rAduction  indiquA  ci-dessous. 

10X  14X  18X  22X 


2BX 


30X 


5? 


12X 


1«X 


20X 


MX 


2iX 


32X 


I 


ails 

du 

idifier 

une 

nage 


errata 
to 


I  palura, 
on  A 


n 


32X 


*«dr 


Tha  copy  filmad  hara  ha*  baan  raproducad  thanks 
to  tha  ganaroaity  of: 

Library  of  Congrass 
Photodupiication  Sarvica 

Tha  imagaa  appearing  hara  ara  tha  bast  quality 
posaibia  considaring  tha  condition  and  laglbility 
of  tha  original  copy  and  in  Icaaping  with  tha 
filming  contract  spacif ications. 


Original  copies  in  printed  paper  covers  ara  filmed 
beginning  with  the  front  cover  and  ending  on 
the  last  page  with  a  printed  or  illustrated  impres- 
sion, or  the  bacic  cover  when  appropriate.  All 
other  original  copies  ara  filmed  beginning  on  the 
firat  page  wKh  a  printed  or  illuatratad  imprea- 
slon,  and  ending  on  the  last  page  with  a  printed 
or  illuatratad  impreaaion. 


The  laat  recorded  frame  on  each  microfiche 
shall  contain  tha  symbol  — ^>  (meaning  "CON- 
TINUED"), or  the  symbol  V  (meaning  "END"), 
whichever  applies. 

Maps,  platea,  charts,  etc.,  may  be  filmed  at 
different  reduction  ratios.  Thoaa  too  large  to  be 
entirely  included  in  one  expoaure  ara  filmed 
beginning  in  the  upper  left  hand  corner,  left  to 
right  and  top  to  bottom,  aa  many  frames  as 
required.  The  following  diagrams  illustrate  the 
method: 


1  2  3 


L'exemplaira  film*  fut  reproduit  grAce  A  la 
gAnArositi  da: 

Library  of  Congress 
Photodupiication  Service 

Las  images  suivantas  ont  tt^  reproduites  avac  la 
plus  grand  soln,  compta  tenu  de  la  condition  at 
da  la  nattet*  de  l'exemplaira  film*,  at  en 
conformity  avac  las  conditions  du  contrat  da 
filmaga. 

Lea  exemplairas  originaux  dont  la  couverture  en 
papier  est  imprimAe  sont  fllmte  en  commen^ant 
par  ie  premier  plat  at  en  terminant  soit  par  la 
darnlAre  page  qui  comporte  une  empreinte 
d'Impression  ou  d'illustration,  soit  par  la  second 
plat,  aaion  Ie  cas.  Tous  las  autras  exemplairas 
originaux  sont  filmte  en  commenpant  par  la 
premiere  page  qui  comporte  une  empreinte 
d'Impression  ou  d'illustretlon  et  en  terminant  par 
la  darnlAre  page  qui  comporte  une  telle 
empreinte. 

Un  dee  symboles  suivants  &pparattra  sur  la 
darnlAre  image  de  cheque  microfiche,  aaion  la 
ces:  Ie  symbole  — ►  signif ie  "A  SUIVRE",  ie 
symbole  V  signifie  "FIN". 

Les  cartes,  planches,  tableaux,  etc.,  peuvent  *tre 
fiimte  *  des  taux  de  reduction  diffirenta. 
Loraque  la  document  eat  trop  grand  pour  Atre 
reproduit  en  un  aaul  cllch*,  11  est  film*  A  partir 
de  I'angle  supArieur  gauche,  de  geuche  A  droite, 
et  de  haut  en  baa,  en  prenant  la  nombre 
d'Images  n*cessaire.  Lea  diagrammea  auivants 
illustrent  la  mAthode. 


1 

2 

3 

4 

5 

6 

III  WriitlliSH 


0^  S'^S 


i 


[Fbom  TBI  AimaoAir  JomwAL  or  Somroi,  Vol.  XXZY,  Jan^  1888.] 


Art.  I. — 7%«  i^^ed  &f  Propagation  of  the  Charleston  Earth- 
quake: disonssed  bv  Profeesor  Simon  Nkwoomb,  IT.  8.  K, 
and  Captain  0.  E.  Dutton,  U.  8.  A.     " 

• 

The  inyestisation  of  the  time  data  of  the  Oharleston  oortib- 
qnake  havinc  been  completed  and  a  final  raralt  being  reached, 
it  is  deemea  proper,  with  the  consent  of  the  Director  of  the 
Oeoloffical  Snrvey,  to  publish  a  brief  abstract  of  the  discossion. 
The  foU  disdunon  will  i^pear  in  the  final  report  upon  the 
earthqoaike,  whidi  re|x>rt  is  now  well  adTanoed  towwd  com- 
pletion. 

Immediately  after  the  earthquake  all  practicable  measures 
were  taken  to  collect  infwmation,  and  specul  effort  was  directed 
to  obtaininff  the  hurgeitt  unount  of  tune  data.  Throuffh  the 
courtesy  of  tiie  AsMdated  Press,  notices  were  publisned  in 
newly  all  tiie  newvpapers  of  the  country  requesting  those  who 
had  made  such  obeervations  to  forward  ti&em  to  the  Director 
of  the  Oeolog^l  Surrey.  Many  per  mis  did  so.  The  Ohief 
Sigmd  Offico*  iiBstmoted  the  observers  ut  that  bureau  who  had 
noted  the  time  of  the  diook  to  report  it,  and  he  forwarded  all 
suo^  reports  to  the  survey.  The  Western  Union  TdeoratA 
Oo.  instructed  its  operators  to  forward  reports  and  rimibr  in- 
structions were  sent  bv  the  Lightbonse  Board  to  light-keepers. 
Spedbl  effort  was  made  to  secure  newspapers  from  as  many 
localities  as  poestbki     Most  of  the  leaaing  papers  of  the 

Ax.  Jooa.  Sot'-TuM*  inns,  Tok  XXX7,  Ha  SOC— lutn  liM 


''^f^t!-M!i^^"^''^--''''''ri'i  ii 


li--iBi.tiwgfe-^\':.w.  !^ 


^--•5^^^?™-  -    " 


■j^wJTviwV-rH^nvifai*  ■>t'^3ri->> 


Newcomh  and  Dution — Speed  of 


> 


country  have  an  agent  or  reporter  at  Washington  and  he  usually 
keeps  a  file  of  the  paper  he  serves.  The  library  of  Congress 
keeps  files  of  two  or  more  papers  from  every  State.  As  many 
of  tnese  as  practicable  were  thoroughly  examined.  Many  local 
papers  were  requested  to  fumitu  copies  of  their  issues  ot  Sept. 
1st,  2d  and  3d,  and  most  of  them  complied.  Many  marked 
copies  of  papers  were  sent  to  the  survey  from  unexpected 
sources.  Altogether  more  than  four  hundred  time  reports 
were  gathered. 

As  might  be  expected  a  portion  of  these  were  useless.  Ini 
order  that  it  may  be  apparent  which  were  selected  for  considera- 
tion and  which  rejected,  the  following  account  is  given.  There 
were  about  thirty  which  stated  that  the  shock  occurred  "  about 
10  o'clock  "  or  "  a  few  minutes  before  10."  As  a  single  min- 
ute is  a  very  important  quantity  here,  all  such  reports  were 
summarily  rejectea  as  too  mdefinite.  The  reports  from  light- 
houses in  most  cases  proved  unavailable.  These  structures 
being  situated  most  frequently  where  access  to  standard  time 
is  difficult,  their  clocks  are  regulated  by  the  sun  and  an 
almanac.  The  uncertainties  of  this  method  of  time  keeping 
were  evidently  too  great  to  justify  any  attempt  to  utilize 
them.  But  a  few  lighthouses  keep  standard  time  and  in  all 
such  cases  their  reports  were  admitted  to  consideration.  There 
were  a  few  (nine  or  ten)  which  gave  times  so  widely  aberrant, 
difFering  by  a  quarter  to  half  an  hour  from  the  great  mass  of 
records,  that  they  were  rejected.  The  whole  number  which 
received  preliminary  consideration  was  316,  many  of  which  it 
was  expected  would  also  be  rejected  after  a  more  thorough 
examination,  due  cause  being  assigned.  These  316  observa- 
tions were  catalogued  in  alphabetical  order,  the  latitudes  and 
longitudes  of  the  localities  being  roughly  ascertained  and  also 
their  distance  from  the  centrum. 

By  far  the  most  important  time  determination  is  that  of  the 
centrum,  which  was  computed  to  be  about  six  seconds  earlier 
than  that  of  Charleston.  The  time  at  Charleston  is  derived  as 
foUowa  Among  the  numberless  clocks  stopped  in  that  city 
by  the  earthquake,  there  were  four  which  had  compensated 
seconds  pendulums  and  second  hands  and  were  of  the  pattern 
generally  classed  as  "  jewelers'  regulators."  All  were  conipared 
daily  with  the  time  signal  of  the  Western  Union  Telegraph  Co., 
and  the  testimony  is  positive  that  none  of  them  had  errors  on 
August  31st  exceeding  nine  seconds,  while  the  mean  probable 
error  of  the  four  was  certainly  much  less  than  this.  The  first 
was  the  regulator  of  James  Allan  &  Co.,  Jewelers,  No.  285 
King  street.  It  was  regulated  by  means  of  a  "  sounder,"  which 
was  daily  put  into  circuit  with  tne  Western  Union  time  signal 
wire.    The  clock  was  corrected  only  when  its  error  exceeded 


ONI 

or^  la  twin 


e  usually 
Congress 
As  many 
any  local 
OT  Sept. 
marked 
expected 
5  reports 

less.  In 
lonsidera- 
.  There 
d  "  about 
[igle  min* 
orts  were 
>m  light- 
tructnres 
iard  time 

and  an 
!  keeping 
;o  utilize 
ad  in  all 
I.  There 
aberrant, 
,t  mass  of 
er  which 

which  it 
thorough 
i  observa- 
^udes  and 

and  also 

lat  of  the 

ids  earlier 

lerived  as 

that  city 


le  jMittem 
compared 
^ph  Co., 

errors  on 
I  probable 

The  first 
3,  No.  286 
sr,"  which 
ime  signal 

exceeded 


W^ 


Propagation  of  the  Vharkston  EaHhquake.  3 

nine  seconds.  Mr.  Allan  is  authority  for  the  statement  that 
its  reading  -next  morning  was  9:51  exactly.  He  had  received 
the  time  signal  on  August  81st,  but  as  the  clock  was  within 
the  limit  of  tolerance  he  did  not  correct  it.  Subject  to  this 
limit  he  had  no  knowledge  of  the  exact  error  of  his  clock  and 
his  memory  on  this  point  did  not  serve  him  The  second  clock 
was  the  regulator  which  controls  the  time  of  the  North  Eastern 
Railway.  This  clock  was  compared  with  the  time  signal  on 
August  3 1st,  but  was  not  corrected,  its  error  being  within  the 
limit  of  tolerance,  which  was  eight  seconds.  It  had  been  reset 
two  days  previously.  Its  reading  was  9:51:15.  It  was  stopped 
by  the  point  of  the  pendulum  catching  behind  the  metallic  arc 
in  front  of  which  it  properly  vibrates.  The  third  clock  was 
that  which  regulates  the  time  of  the  Charleston  &  Savannah 
Railroad.  It  had  been  reset  two  days  previously  and  compared 
with  the  time  signal  on  August  Slst,  and  was  within  the  limit 
of  tolerance,  eight  seconds.  Its  reading  was  9:51:16  and  it  was 
stopped  in  the  same  manner  as  the  preceding  one.  The  fourth 
clock  was  that  of  the  South  Carolina  Railroad.  It  had  been 
reset  by  the  daily  time  signal  on  the  day  of  the  earthquake. 
Its  reading  was  9:51:48. 

Although  these  records  range  through  an  interval  of  48 
seconds  they  may  be  reconciled.  The  azimuths  of  the  planes 
of  oscillation  of  their  pendulums  were  as  follows : 

James  Allan  &  Co's N.  85°  E. 

North  Eastern  Railroad N.  40»  E. 

Charleston  &  Savannah  Railroad N.  66°  E. 

South  Carolina  Railroad N.  30°  W. 

These  azimuths  may  be  put  into  relation  with  what  is  now 
known  concerning  the  varying  phases  of  the  shocks,  their 
respective  durations  and  directions  of  vibratory  motion.  The 
earthquake  at  Charleston  began  as  a  light  tremor,  steadily  in- 
creasing in  power  through  an  interval  estimated  to  be  fron^  10 
to  15  seconds'  duration ;  then  suddenly  or  by  swift  degrees  it 
swelled  into  the  full  power  of  the  first  maximum,  then  sub- 
sided to  a  minimum,  then  swelled  suddenly  to  a  second  maxi- 
mum and  lastly  died  away  gradually.  The  interval  from  the 
beginning  of  the  first  maximum  to  the  close  of  the  second 
maximum  is  estimated  at  from  35  to  65  seconds ;  the  subsid- 
ing tremors  are  estimated  at  about  6  to  8  seconds :  the  total 
duration  from  66  to  75  seconds.  It  may  be  exptreseed  graphi- 
cally by  the  following  curve  in  which  the  abscissas  represent 
time  and  the  ordinates  an  arbitrary  scale  of  intensity. 

In  the  first  maximum  the  waves  were  mainly  normal  and 
came  from  N.  30°  W.  In  the  second  maximum  the  direction 
of  vibration  was  abtfut  at  right  angles  with  the  foregoing  or 


f\r'J 


Ji:•^^^ 


4  Newcomb  and  Dutton — Speed  of 

about  N.  60°  E.  It  Mrill  now  be  Been  that  the  planes  of  oscil- 
lation of  the  first  three  clocks  made  wide  angles  with  the  di- 
rection of  motion  of  the  first  maximum,  while  the  plane  of  the 
fourth  clock  was  almost  exactly  parallel  with  that  direction  and 
perpendicular  to  the  direction  of  motion  of  the  second  max- 
imum.   The  fourth  clock,  then,  may  easily  have  escaped  arrest 


thSlm        Mm  to*         Sim  SOi         51m  aoi         51m  M         Bim  lOi  aim 

until  the  second  maximum  while  the  other  three  would  have 
little  chance  of  escaping  the  first  maximum,  even  if  they  did 
not  stop  during  the  lighter  preliminary  tremors.  That  the  sec- 
ond and  third  clocks  stopped  during  the  first  maximum  is  ren- 
dered probable  by  the  way  in  which  their  pendulums  were 
caught.  It  would  require  a  considerable  acceleration  in  a  di- 
rection perpendicular  to  their  planes  of  oscillation  and  at  times 
when  the  pendulums  were  near  the  extremities  of  their  arcs  of 
vibration  in  order  to  throw  their  bobs  far  enough  backward  to 
catch  in  the  manner  they  did.  These  two  clocks  are  relied 
upon  as  giving  the  time  of  the  first  maximum.  The  chances 
are,  however,  that  the  pendulums  were  not  caught  in  this  par- 
ticular way  during  the  first  three  or  four  oscillations,  but  went 
staggering  along  for  a  very  few  beats  until  finally  caught.  An 
interval  of  three  or  four  seconds  was  probably  occupied  in  the 
rapid  swelling  of  the  quake  from  the  preliminary  milder  phase 
into  the  full  power  of  the  maximum.  If  we  assume  for  the 
beginning  of  the  first  maximum  an  instant  of  time  about  three 
or  four  seconds  earlier  than  that  indicated  by  the  two  railroad 
clocks,  i.  e.  9:51:12,  our  actual  error,  it  is  believed  will  not 
exceed  four  seconds.  The  clock  of  James  Allan  &  Co.  prob- 
ably stopped  at  a  slightly  earlier  phase.  If  it  may  be  assnmed 
to  have  oeen  six  or  eight  seconds  slow,  its  stopping  would  have 
been  easily  possible  at  that  phase;  for  many  less  sensitive 
clocks  throughout  the  country  were  arrested  by  tremors  no 
more  forcible  than  those  in  Charleston  at  the  particular  phase 
thus  indicated.  We  shall  reach  the  same  result,  9:51:12,  if 
we  throw  out  the  fourth  clock  as  relating  to  the  second  maxi- 
mum end  (giving  the  weight  2  to  both  the  second  and  third 
clocks  and  tiie  weight  1  to  the  first)  take  the  mean  readings  of 
the  three.  The  whole  tenor  of  the  evidence  from  other  clocks 
in  Charleston  points  strongly  to  a  time  a  few  seconds  later  than 
9:51  for  the  first  maximum. 

It  is  plainly  necessary  to  select  some  phase  of  the  earthquake 
in  Charleston  or  at  the  centmm  as  the  oeginning,  with  which 
the  beginning  in  all  other  places  must  be  compared.    It  must 


% 


Propagation  of  the  Charleaton  Earthquahe.  8 

plainly  be  a  phase  at  which  the  shocks  had  very  great  power, 
sufficient  to  make  themselves  felt  hundreds  of  miles  away. 
This  phase  should  obviously  be  that  which  han  Ijeen  called  the 
beginning  of  the  first  maximum.  It  still  remains  to  find  the 
corresponding  time  at  the  centrum.  As  the  speed  of  propaga- 
tion is  now  known  to  have  been  in  the  neighoorhood  of  three 
miles  a  second  and  as  the  distance  of  Charleston  from  the 
theoretic  centrum  is  20  miles,  the  subtraction  for  the  time  at 
the  centrum  is  taken  to  be  six  seconds,  making  the  time  of  be- 
ginning at  that  point  9:51:06  standard  time  of  the  75th 
meridian. 

The  full  catalogue  was  next  examined  in  order  to  ascertain 
what  reports  should  be  finally  rejected.  In  the  final  report 
this  catalogue  will  be  published,  together  with  a  list  of  the 
rejected  observations  showing  the  grounds  of  rejection.  For 
present  purposes  a  summary  view  of  these  reports  is  given, 
showing  the  number  of  observations  correspondmg  to  specific 
minutes  or  falling  betweeen  consecutive  minutes. 

Table  showing  the  numbers  of  reports  corresponding  to  specified 
minutes  or  falling  between  consecutive  minutes. 

9:47  and  seconds 1 

9:48 --   3 

9:50 82 

9:51 6 

9:51  and  seconds 6 

9:62 26 

9:52  and  seconds 9 

9:53 28 

9:53  and  seconds ^6 

>-:54 31 

9:64  and  seconds 9 

9:55 f6 

9:65  and  seconds 8 

9:66 21 

9:66  and  seconds 2 


9:67 

9:58 

9:58  and  seconds • 

9:39 

10:00 13 

10:01 2 

10:02 -. 1 


Total . 


316 


There  are  thus  four  reports  giving  times  earlier  than  9:50  and 
three  later  than  10  o'clock.  The  synopsis  illustrates  well  the 
tendency  of  people  to  give  time  in  terms  which  are  multiples 


6 


NevBComh  and  Dntton — Speed  of 


of  five  minutes.  Thus  we  have  32  giving  9:50,  but  none  giv- 
ing 9:49,  and  only  six  giving  9:51.  There  are  13  giving  10 
o'clock  and  tliere  would  have  been  many  more  of  them  if  the 
catalogue  had  included  those  which  stated  the  time  as  being 
"about"  10  o'clock  or  "near"  10  o'clock.  There  are  8fi,  or 
more  than  one  fourth  the  whole  number,  which  give  9:56. 
Every  one  of  the  9:50  reports  is  rejected.  It  is  certain  that 
they  all  involve  errors  greater  than  one  minute  too  early,  and 
the  large  number  of  them  would  introduce  a  large  systematic 
error  into  the  mean  ;  and  as  there  is  no  apparent  reason  for  re- 
jecting or  keeping  one  observation  rather  than  another,  all  of 
them  are  thrown  out.  All  of  the  10  o'clock  observations  are 
thrown  out.  For,  upon  further  examination,  all  giving  9:58  and 
seconds,  9:59,  10:01  and  1():02  will  be  rejected  on  their  merits. 
This  would  leave  the  10  o'clock  reports  as  an  isolated  group  in 
an  otherwise  comparatively  orderly  series,  and  its  eflfect  would 
be  to  introduce  an  error  of  unknown  magnitude  and  of  anoma- 
lous character.  In  dealing  with  those  giving  9:55  there  is 
more  difficulty.  The  following  course  has  been  adopted. 
Wherever  a  report  states  clearly,  or  raises  a  strong  presump- 
tion, that  this  was  really  the  nearest  minute  observed,  to  the 
exclusion  of  any  other,  it  is  accepted  if  otherwise  unobjection- 
able. Where  this  evidence  is  wanting  the  report  is  rejected. 
It  is  quite  probable  that  some  thus  rejected  are  very  good  ob- 
servations ;  but  it  is  clearly  better  to  reject  many  possiblv  good 
observations  (provided  a  sufficient  number  remain)  than  to 
admit  a  few  bad  ones  with  the  certainty  of  introducing  an  un- 
known error.  The  number  of  9:65  reports  thus  rejected  is  43, 
which  happens  to  be  just  one  half. 

Still  otner  ol)servations  are  rejected  on  their  merits.  A  ma- 
jority of  these  are  thrown  out  for  what  are  presumed  to  be 
large  xmexplained  errors.  There  are  29  of  them,  of  which  15 
are  rejected  for  being  two  minutes  or  more  too  early  and  14 
for  being  as  much,  or  more  than  as  much,  too  late,  when  com- 
pared with  a  larger  number  of  much  better  observations  in  the 
same  locality  or  in  the  immediately  surrounding  region.  The 
rejection  of  these  29  observations  does  not  greatly  affect  the 
deduced  speed,  but  it  does  diminish  notably  the  computed 
probable  error.  The  total  number  rejected  for  all  causes  is 
130  and  the  number  accepted  is  186.  These  have  been  sepa- 
rated into  four  groups,  each  containing  data  which  are  consid- 
ered to  be  as  nearly  nomogeneons  as  possible ;  that  is  to  say,  in 
each  group  the  observations  are  presumed  to  have  the  same 
sources  of  error,  whether  accidental  or  systematic. 

The  first  group  is  required  to  fulfill  the  following  condi- 
tions :  (1)  The  report  must  specify  the  beginning,  or  the  time 
when  the  tremors  first  became  sensible.    (2)  It  must  give  not 


Propagation  of  the  Charleston  Eart/ujuake. 


[none  jfiv- 

ving  10 

ui  it  the 

R8  being 

|ire  80,  or 

ve  9:65. 

rtain  that 

early,  and 

iystematic 

on  for  re- 

ler,  all  of 

ations  are 

g  9:58  and 

eir  merits. 

1  group  iu 

feet  would 

of  anotna- 

)5  there  is 

adopted. 

presnmp- 

ired,  to  the 

lobjection- 

s  rejected. 

ygood  ob- 

sBibly  good 

in)  than  to 

»ng  an  nn- 

ected  is  43, 

ts.  A  ma- 
imed  to  be 
:  which  15 
rly  and  14 
when  com- 
tions  in  the 
gion.  The 
affect  the 

I  computed 

II  causes  is 
been  sepa- 
are  consid- 
is  to  say,  in 
)  the  same 

xring  condi- 
or  the  time 
it  give  not 


only  the  minutes, 'but  also  the  seconds,  with  an  uncertainty  not 
exceeding  15  seconds.  (3)  It  must  have  been  obtained  from  a 
clock  kept  running  with  accuracy  upon  standard  time  or 
equally  reliable  local  time,  or  fronj  a  clock  or  watch  compared 
with  such  time  within  a  few  hours  of  the  occurrence.  There 
are  five  observations  besides  that  of  Charleston  which  meet 
these  re(|uirements. 

The  second  group  will  consist  of  those  which  fulfill  the  same 
conditions  as  the  first,  except  that  they  will  be  refjuirud  to  give 
only  the  mincte  or  half  minute  nearest  to  the  begiiming. 
There  are  eleven  which  answer  to  these  requirements. 

The  third  group  will  include  all  that  reiuaiu  after  taking  out 
groups  I,  II,  and  the  6toppe<l  clocks.  Some  of  these  state  that 
the  time  is  that  of  the  beginning,  but  fail  to  show  that  any  attempt 
was  made  to  ascertain  the  error  of  the  time-piece.  Some  give  a 
satisfactory  account  of  the  time-piece,  but  tail  to  state  the  phase 
to  which  the  reported  time  refers.  Many  do  neither  the  one 
nor  the  other.     The  number  of  reports  in  this  group  is  125. 

The  fourth  group  consists  of  accepted  reports  of  clocks 
stopped  by  the  first  great  shock.  The  clocks,  lio^'^ver,  must 
be  stated  to  have  been  regulated  carefully  by  standard  time  or 
by  local  time  known,  to  be  equally  accurate. 

In  all  the  groups  there  is  more  or  less  discordance  among  the 
several  observations,  no  two  giving  the  same  speed.  As  the 
errors  of  the  first  two  groups  are  beueved  to  be  inainly  of  the 
accidental  class,  the  best  method  seems  to  be  to  submit  them 
to  the  process  of  least  squares.  The  equations  of  condition 
may  be  formed  verv  simply  in  the  following  manner:  The 
computed  time  of  the  beginning  at  the  centrum  (which  has  already 
been  given)  must  be  presumed  to  have  some  error,  which  may  be 
designated  by  x.  If  <,  be  the  computed  time  at  the  centrum 
(9:51:06)  and  t  the  reported  time  at  any  other  locality,  then 
\t—t^  —  the  number  of  seconds  in  the  observed  time-interval 
taken  by  the  wave  to  travel  from  the  centrum  to  the  place  of 
observation.  If  j9  be  the  distance  in  statute  miles,  and  y  the 
number  of  seconds  or  fraction  of  a  second  required  to  travel  one 
mile,  we  may  form  the  following  equation :  aj+Dy=<— <„  in 
which  there  are  only  two  unknown  quantities,  x  and  y.  This 
implies  that  the  speed  is  uniform.  If  this  implication  differs 
widely  from  the  truth,  indications  of  it  may  be  expected  to 
appear  in  the  residuals.  It  is  necessary  to  put  the  equations  of 
condition  into  a  form  in  which  a  time  and  not  a  speed  shall  be 
the  unknown  quantity,  because  the  times  and  not  the  distances 
are  the  data  into  which  the  greatest  uncertainty  enters.  If, 
putting  V  for  the  speed  of  transmission,  we  put  our  equations 
mto  the  form  of  v{t  —  t,)=D,  they  would  be  subject  to  the 
objection  that  their  uncertain  quantities  would  be  the  coeffi- 


8 


NetPoomb  and  DutUm — Speed  qf' 


cientH  of  the  unknown  (juantities  imd  not  the  absolute  tenns. 
The  distances  from  the  centrum  have  been  taken  from  the 
Land  Oftice  map  of  the  United  States  by  measurement  with  a 
scale.  They  are  subject  to  pt)88ible  errors  as  great  as  three  or 
four  miles,  but  this  error  is  so  sniall  in  comparison  with  tlie 
best  times  that  the  distances  may  be  regarded  as  sensibly  exact. 
The  following  reports  constitute  the  first  group.  For  the 
sake  of  brevity  the  full  accounts  of  these  reports  are  here 
omitted.    They  will  appear  in  the  final  work  on  tne  earthquake. 

Grout  I. —  The  best  Observations. 


Looklltjr.               Sfate. 

Dtitance. 

Time  ah.f 
m.        «. 

Weight.                ObMiTcr. 

Centrum,          S.  C. 

0 

61     06 

2 

Washington,   D.  C. 

4S2 

63     20 

2        Prof.  Newcorab 

Washington,   D.  C. 

462 

63     23 

2        Alex.  McAdie. 

Baltimore,         Md. 

487 

63     20 

1        R.  Randolph. 

New  York,      N.  Y. 

646 

64     30 

2        M.  C.  Whitney. 

Dyersburg,      Tenn. 

669 

64     00 

1        Louis  Hughes. 

From  these  observations  the  following  equations  of  condition 

may  be  formed. 

wt. 

BMid. 

X   + 

Oy  = 

0          2 

—  2-6 

X   + 

462y  = 

1356       4 

+  1-6 

X  +  487y  = 

134           1 

+13-9 

X  -+-  869y  = 

174           1 

-   0-8 

x  + 

646y  = 

204          2 

-   7-8 

By  the  process  of  least  squares  the  normal  equations  are : 

lOaj  +         4164  =       1268 
4164a;  -{-  2210196  =  672408 

The  solution  is,  »  =  -  2-68  ±  4-7s.  and  y  =  0-309  db  0  Ol! 
The  resulting  speed  is,  3-236  ±  0-106  miles  or  5205  ±  168 
meters  per  second. 

Group  II. —  Good  reports,  giving  the  time  of  beginning  to  the 
,     nearest  minute  or  half  minute. 

Localltr. 

Centrum, 

Nashville, 

Covington, 

Pikesville, 

Evansville, 

Cle\  eland, 

Cleveland. 

Crawfordsville, 

Belvidere, 

New  York, 

Stockbridge, 

Albany, 


SMte. 

Distance. 

Time. 

Weigh 

ObserTcr. 

s.  c. 

0 

61™06' 

2 

Tenn. 

43b 

63  30 

J.  D.  Leonard. 

Ky. 

488 

63  41 

JoB.Brook8haw. 

Md. 

490 

53  30 

C.  R.  Goodwin. 

Ind. 

645 

64 

P.  W.  Norton. 

O. 

604 

54 

Wm.  Line. 

O. 

604 

54 

G.  H.  Tower. 

Ind. 

620 

t>4 

i 

E.  C.  Simpson. 

N.  J. 

622 

54 

G.  W.  Holstein. 

N.  Y. 

646 

64  30 

N.  Y.  Herald. 

Mass. 

765 

66 

i 

J.  0.  Jacot. 

N.  Y. 

770 

£6 

1 

W.  G.  Tucker. 

Propagation  of  the  Charleston  Earthquake. 


uto  temiB. 
I  from  the 
ant  with  a 
IB  tliroe  or 
in  with  tlie 
iibly  exact. 
.  For  tlie 
B  are  hero 
larthquake. 


ObMiTcr. 

.  Newcorab 
.  McAdie. 
landolph. 
).  Whitney. 
8  Hughes. 

f  condition 


From  these  wo  may  form  the  following  equations. 


»DB  are: 


109  dt  0  Ol! 
S205  ±  168 

ning  to  the 


.  Leonard. 
Brookshaw. 
,.  Goodwin. 
i.  Norton. 
.  Line. 
[.  Tower. 
'.  Simpson. 
V.  Holstein. 
r.  Herald. 
.  Jacot. 
3.  Tucker. 


Weight. 

RcildnMli 

«  -f        Of/  =        0 

2 

-    1-6 

X  -j-  438»/  =    144 

1 

-    9-8 

X  +    4H8v  =:    165 

1 

—  6-3 

X  +  49(\v  =   144 

1 

+   6-3 

X  +   fi4Sy   =    174 

1 

—   06 

X  +   604.y   =    174 

2 

-fll-6 

X  4-   620.»/  =    174 

i 

+  16'6 

X  +  tt22y  =   174 

1 

-I-17-2 

X  -f   646.V  =   204 

1 

-   6-6 

X  +   76fty  =  294 

i 

-68-4 

X  +    770y  =  234 

1 

+  31 

The  normal  equations  are  : 

12  «  +  6898-5  y  =  1811. 
6898-6a;  -f-  3677366-6  y  =  1100677. 

The  solution  gives  x=  -  1-6b.  db  7'7b.  y  =  0'31  ±  0-014s. 
The  resulting  speed  is,  8-226  ±  0147  miles  or  6192  ±  236 
meters  per  second. 

Group  III  consists,  of  reports  which  fail  to  give  either  the 
means  of  judging  of  the  comparative  accuracy  of  docks  and 
watches  or  of  determining  to  what  phase  the  observation  re- 
fers. Many  and  indeed  the  majority  of  them  are  defective  in 
both  of  these  respects.  Quite  probably  some  of  them  are  good 
observations  but  fail  to  give  the  evidence  of  it.  So  far  as 
errors  of  clocks  and  watches  are  concerned  the  errors  nky  be 
considered  as  belonging  to  the  accidental  class.  But  all  errors 
as  to  the  phase  must  be  systematic.  That  some  of  them  refer 
to  more  or  less  advanced  phases  Ib  certain,  and  it  becomes 
difficult  to  determine  how  many  of  them  do  so,  and  how 
great  is  the  average  tardiness.  It  is  obvious  that  the  effect  of 
all  such  errors  is  to  make  the  time  too  late  and  the  resulting  speed 
too  slow.  The  general  indications  are,  however,  that  this  system- 
atic error  is  not  a  large  one.  By  comparing  miscellaneous 
reports  from  those  cities  which  have  also  given  better  verified 
repoits  belonging  to  groups  I  and  II  there  seems  to  be  a  ten- 
dency of  the  averaf^e  value  of  this  error  to  fall  between  one- 
tenth  and  one-twentieth  of  the  mean  value  of  the  time-interval. 

In  discussing  this  group  it  seems  unnecessary  to  go  to  the 
length  of  formulating  a  hundred  equations  of  condition,  and  an 
equally  good  result  or  even  a  better  one  may  be  obtained  by  the 
following  moi-e  summary  process.  We  may  take  them  in  sets, 
the  first  of  which  shall  comprise  all  times  within  200  miles  of 
the  centrum,  the  second  set  all  between  200  and  800  miles,  the 
third  all  between  800  and  400  miles,  and  so  on  lutil  the  last. 


10 


Newcomh  and  Dutton — Speed  of 


which  shall  compriee  all  beyond  800  miles.  In  each  set  we  may 
then  take  the  weighted  arithmetic  means  of  the  times  and  dis- 
tances as  if  they  were  single  observations. 

Gboup  III. — List  o/'126  miscellaneous  Time  Reports. 


Locality. 

state. 

Dlstnnce. 

Time.     W't.           BemarkB. 

Statesburg, 

ao. 

80 

51  "SO*     I 

Coluin1)ia, 

S.O. 

89 

52             1 

SaTunnnh, 

Ga. 

89 

61  63      2 

mean  of  3  ohs. 

Augusta, 

Ga. 

ill 

61  30      2 

mean  of  2  obs. 

Laurinburg, 

N.  C. 

135 

51             I 

Dnrien, 

Ga. 

138 

52  30      1 

Brunswick, 

Ga. 

165 

62             I 

Macon, 

6a. 

203 

52             1 

Jacksonville, 

Fla. 

211 

52             2 

mean  of  3  obs. 

Fernandina, 

Fla. 

225 

63             ] 

Olustee, 

Fla. 

355 

53             1 

Palatka, 

Fla. 

255 

53             1 

Thtimasjville, 

Ga. 

273 

62  20      1 

Wytheville, 

Va. 

284 

62  27       1 

Knoxvillo, 

Teun. 

302 

54            J 

Zellwood, 

Fla. 

80t> 

53             1 

Chattanooga, 

Tenn. 

329 

63             1 

Norfolk, 

Va. 

349 

54            1 

University, 

Ala. 

363 

52             1 

Ashland, 

Va. 

367 

62             1 

Shelby  Iron  Works, 

Ala. 

377 

5t            1 

Catiettsburg, 

Ky. 

406 

52  30      1 

mean  of  2  obs. 

Pungoteague, 

Va. 

410 

53             1 

Decatur, 

Ala. 

412 

63            ] 

Iron  ton, 

0. 

414 

56             1 

Nashville, 

Tenn. 

438 

54  30      ] 

WHshinjrton, 

D.  C. 

452 

63  41      'a 

:    mean  of  4  obs. 

Louisville, 

Ky. 

486 

64  38      1 

mean  of  2  obs. 

Baltimore, 

Mi 

487 

53             1 

Dayton, 

Ky. 

487 

54  11      1 

Newport, 

Ky. 

488 

53  21 

Cincinnati, 

0. 

491 

63  41      ' 

V    mean  of  6  obs. 

Lancaster, 

0. 

491 

54 

Wyoming, 

0. 

601 

63  41 

ColumbuB, 

0. 

513 

63  41 

!    mean  of  4  obs. 

HamUtoo, 

0. 

513 

64  11 

Paris, 

Tenn. 

620 

66 

Pittsburg, 

Pa. 

626 

64  30 

I    mean  of  2  obs. 

Brookville, 

•Ind 

626 

63 

New  Philadelphia, 

0. 

632 

64 

Sewickly, 

Pa. 

536 

64 

Mt.  Vernon, 

0. 

636 

66 

Wellsville, 

0. 

538 

66 

Oxford, 

MiBB. 

548 

66 

Paducah, 

Ky. 

668 

62  16 

Philadelphia, 

Pa. 

566 

63 

Burlingto::, 

N.J. 

634 

63 

Indianapolis, 

Ind. 

584 

65 

i    mean  of  3  obs 

Cairo, 

ni. 

588 

63 

Titusville, 

Fa. 

6U8 

66 

Helena, 

Ark. 

609 

65 

Toledo, 

0. 

657 

66 

Newark, 

N.J. 

640 

53 

Jamestown, 

N.  T. 

642 

66 

Propagation  of  the  Charleston  Earthquake.  11 


let  we  may 
)8  and  dis- 


forta. 

rk*. 


1  obs. 

2  obs. 


t  obs. 


i  oba. 


1  obs. 
i  obs. 


Sobs. 
4  obs. 
2  obs. 


3  obs. 


Remarks, 
moan  of  4  good  obs. 
mean  of  10  obs. 


mean  of  6  oba. 

mean  of  2  obs.- 
mean  of  2  good  obs. 


Locality.  State.  Distance.  Time.     W't. 

Brooklyn.  N.  Y.  643  54'>'30'     3 

New  York,  N.  Y.  646  64  12      6 

Haokensack,  N.J.  664  54 

Warwick,  N.  Y.  661  56 

Oowanda,  N.  Y.  666  66 

Detroit,  Mich.  675  56  12 

Valparaiso,  Ind.  705  53 

London,  Ont.  706  56 

Peoria,  111.  710  55 

New  Haven,  Conn.  711  56  30 

Port  Huron,  Mich.  712  66 

Hudson,  N.  Y.  747  57 

Hartford,  Conn.  747  54  46 

Stuyvesant,  N.  Y.  760  57 

East  Saginaw,  Mich.  766  68 

Albany,  N.  Y.  770  56  40 

Fonda,  N.  Y.  776  65 

Saratoga,  N.  Y.  797  53 

Greenfield,  Mass.  799  66 

Keokuk,  Iowa.  810  56            2     2  obs. 

Dighton,  Mass.  812  56 

Davenport,  la.  827  55 

r^e  Placid.  N.  Y.  827  66 

Jamaica  Plain,  Mass.  828  57 

Blue  Mt.  Lake,  N.  Y.  830  56 

Bellows  Falls,  Vt.  832  63 

Boston,  Mass.  832  55  30      12  obs. 

Dubuque,  la.  ■  878  57 

Prairie  du  Chien,  Wis.  924  66  30 

,  Taking  these  in  groaps  in  the  manner  just  indicated  we  have: 

WelBht.  Residuals. 

Centrum  «  +  Oy  =   0    2    +  406 

Oto  155  X  +  11 '.y  =  3»     ® 

203  to  284  X   +  240y  =84     8 

302  to  377  X   +  342y  =  122     7 

405  to  491  X   4-  462y  =  158    16 

601  to  588  X  -h  642y  =  184    18 

608  to  675  X  +  647y  =  217    20 

705  to  799  X   -f  744y  =  255    15 

810  to  924  X   4-  8:{7y  =  278    11 


1-90 

—  -28 

—  4-43 

—  -60 

—  -05 
+    1-80 

—  4-00 
+  3-85 


The  normal  equations  are : 

10635  +  65768y  =  18940. 
66768a!  +  34474772.y  =  11668675. 

The  solntion  give^  »  =+  4-06  ±  IT  seconds,  y  =  0-3319  ± 
0-0039.  The  resulting  speed  is,  3-013  ±  0-027  miles  or  4848 
±  43  metres  per  second.  To  this  result  some  correction  must 
be  applied  for  the  systematic  error,  which,  as  already  stated, 
there  is  reason  to  believe  probably  lies  between  one-tenth  and 
one-twentieth  of  the  mean  time-interval  and  therefore  of  the 
speed.  Suppose  it  be  taken  at  one-lifteenth  of  the  amount, 
with  a  probable  error  of  one  third  of  the  correction.    This 


-.•«|liM*Mpk 


12 


Newcomh  and  DntUm — Speed  of 


:  0-072  miles  or  5171 


would  make  the  corrected  result  3 '2 14 
d=  116  metres  per  second. 

Stopped  Clocks. 
It  is  natural  to  suppose  that  if  a  clock  were  stopped  by  an 
earthquake  and  if  its  error  at  the  time  were  known  it  would 
give  the  best  possible  record  of  the  time  of  advent  of  the  shock. 
An  examination  of  the  time  reports  of  this  earthauake,  how- 
ever, strongly  contradicts  this  conclusion.     A  clock  may  stop 
at  almost  any  phase  of  the  disturbance.    A  sensitive  one  may 
pass  tlirough  an  earthquake  of  considerable  violence  and  not 
stop  at  all.     A  jeweler's  clock  in  Charleston  was  found  goinff 
the  next  morning,  and  when  the  telegraph  wires  were  re-opened 
its  error  was  found  to  be  small,  showm^  that  its  escapement  had 
missed  very  few  beats,  if  any.    Clocks  in  Columbia,  Savannah, 
Augusta  and  Wilmington,  'N.  C,  in  many  cases  kept  gomg 
Inquiry  at  Wilmington  elicited  the  reply  that  no  iewelers 
clocks  had  been  stopped.     Several  reports  describe  clocks  whose 
rates  are  satisfactorily  vouched  for  but  whose  times  can  be  ac- 
counted for  only  upon  the  theory  that  they  were  stopped  by 
the  second  powerful  shock,  which  was  felt  at  Charleston  about 
five  minutes  after  the  principal  one,  e.  g.y  Branchville,  S.  C., 
Augusta,  Rome,  Ga.,  Cape  Canaveral,  Camden,  Ala.,  Memphis, 
Tenn.    There  are  some  cities  where  the  time  of  beginning  is 
well  established  by  independent  observation  and  which  also  reh 
port  stopped  clocks.    In  every  such  case  the  time  of  the  stopj^d 
clock  is  much  later.     Thus  at  Nashville  the  time  of  beginniM 
was  noted  by  a  clock  which  continued  going  for  42  seconds 
and  then  stopped.    Similar  means  of  comparison  come  from 
Cincinnati,  Covington,  Ky.,  Pittsburg,  Newark,  N.  J.,  Brooklyn 
and  New  York.    And  in  general  wherever  stopped  clocks  can 
be  compared  with  really  good  personal  observations  theymvan- 
ably  show  a  later  time  and  usually  a  much  later  one.    The  dif- 
ference is  plainly  due  to  the  fact  that  it  generally  takes  a  con- 
sideK3,ble  time  and  an  accumulation  of  the  effects  of  the  vibra- 
tions  of  the  building  upon  the  pendulum  to  stop  a  clock.     An 
attempt  has  been  maae  to  evaluate  this  difference  by  taking 
those  cases  where  a  comparison  can  be  made  between  the  read- 
ings of  stopped  clocks  and  independent  detenninations  of  the 
times  of  the  beginning  in  the  same  locality. 

liOOalttr. 

Nashville, 

Covington, 

Cincinnati, 

Pittsburg, 

Brooklyn, 

New  York, 


State. 

Tenn. 

O. 
P». 
N.  Y. 
N.  Y. 


Intenrali  by 

penoDftl  o^•. 

Beoondi. 

144 


■toi 


InterrsU  bj 
ipped  cIocKR. 
Becondt. 


155 
155 
174 
204 
204 
Mean  ratio, 


186 
235 
106 
284 
284 
249 


BatlM.    Welghta. 

1-29  2 

1 

1 

1 

1 

1 

1 


52 
'26 
34 
•15 
•22 
•28 


1 
2 
1 
1 
2 


es  or  6171 


ped  by  an 
rn  it  would 
the  shock, 
nake,  how- 
may  stop 
one  may 
ce  and  not 
)und  goinj 
e  re-openei 
pement  had 
,  Savannah, 
kept  going, 
ao  jewelers' 
locKS  whose 
9  can  be  ac- 
stopped  by 
eston  about 
iville,  S.  a, 
.,  Memphis, 
)eginning  is 
nich  also  ra- 
the stop^d 
if  beginnmg 
42  seconds 
come  from 
r.,  Brooklyn 
[  docks  can 
they  invari- 
8.    The  dif- 
lakes  a  con- 
if  the  vibra- 
clock.    An 
e  by  taking 
len  the  rea£ 
.tioBs  of  the 


Ratio*. 

1-29 
1-52 
1*26 
1-34 
1'15 
1-22 
1-28 


WeicfaU. 
2 

1 

2 
I 
1 
2 


Propagation  of  the  Charleston  Earthquake. 


13 


In  the  above  table  the  comparison  at  Cincinnati  takes  account 
only  of  a  single  clock,  whose  error  happened  to  be  known  ex- 
actly. The  time  of  beginning  in  that  city  is  also  known  with 
exceptional  certainty  and  accuracy.  It  will  not  differ  more 
than  eight  or  ten  seconds  from  9h.  1 6m.  (Cincinnati  local 
mean  time  or  9h.  58m.  41s.).  If  we  consider  Cincinnati  and 
suburban  towns  within  fifteen  miles  of  the  city  which  are 
supplied  with  local  time  from  the  Cincinnati  observatory,  we 
have  no  less  than  twenty-two  time  reports,  of  which  nine  are 
stopped  clocks.  Two  personal  observations  giving  9:15  local 
have  been  rejected  because  they  are  multiples  ot  five.  One 
report  giving  9:17:45  has  been  rejected  because  its  author,  be- 
siaes  indicating  that  it  refers  to  an  advanced  phase,  throws 
doubt  on  his  own  observation.  Of  the  remaining  ten  personal 
observations  one  gives  9:15:40,  eight  give  9:16,  and  one  gives 
9:16:80.  Of  the  stopped  clocks,  three  were  in  the  centr^  of- 
fice of  the  Western  tjnion  Telegraph  Co.  They  kept  standard 
time  and  were  read  only  to  the  nearest  minute.  AU  three  are 
reported  to  have  stopped  at  9:54.  The  clock  in  the  fire  tower 
is  the  one  whose  error  was  known.  Its  corrected  reading  was 
9:16:40.  The  remaining  docks  gave  (9:16).  (9:16),  (9:17),  (9: 
17:20),  and  (9:19).  Four  of  the  latter  were  irom  the  suburban 
town  of  Lockland  Reducing  to  standard  time  and  taking  their 
mean,  the  ratio  of  the  time-interval  by  stopped  clocks  to  that 
by  personal  observation  is  1.26,  a  result  identical  with  that  de- 
rived from  the  clock  in  the  fire  tower  alone  and  nearly  the 
same  as  that  in  the  tabla  There  is  reason  to  believe,  however, 
that  this  ratio  is  a  little  too  great  for  the  mean  of  stopped 
docks  throughout  the  entire  country,  and  especially  so  for 
those  of  very  distant  localities ;  for  if  the  ratio  were  uniform, 
the  absolute  differences  between  the  two  kinds  of  data  would 
be  very  wide  in  remote  regions  and  small  near  the  centrum. 
This  is  not  the  case.  The  absolute  differences  at  very  remote 
localities  are  very  little,  if  any,  greater  than  those  at  the  middle 
distances.  This  difficulty  prevents  us  from  assigning  any 
spedfic  value  to  the  correction  and  from  determining  its  prob- 
able error.  iNeverthelees  the  comparisons  just  made  inaicate 
that  the  systematic  error  is  probably  of  such  magnitude  that,  if 
due  allowance  were  made  tor  it,  tne  corrected  result  for  the 
topped  docks  would  not  differ  much  from  those  of  the  i>re- 
cedinf^  groupa  While  this  group  furnishes  evidence  which 
strongly  supports  the  approximate  correctness  of  the  results  of 
the  other  turee  it  cannot  be  a  source  of  greater  precision  nor 
can  it  famish  the  means  of  reducing  the  final  probable  error. 


14 


Newcmnh  and  Dutton — Speed  of 


LOCKlltf. 

Centrum, 

Charleston, 

Columbia, 

Savannah, 

Langley, 

Au}!U8ta, 

Cochran, 

Macon, 

Jacksonville, 

Atlanta, 

Catlettsbarg, 

Nashville, 

Columbus, 

Covington, 

Cincinnati, 

Cincinnati, 

Meridian, 

Locktand, 

Havre  de  Grace, 

Pittsbnrg, 

Newcastle, 

Atlantic  City, 

Wooster, 

Newcastle, 

Indianapolis, 

Memphis, 

Cairo, 

Meadville, 

Newark, 

Brooklyn, 

New  York, 

Ithaca, 

Manistee, 


Gboup  IV, 

SUte. 

s.  c. 

S.  C. 

s.  c. 

6a. 

s.  c. 

Ga. 

Ga. 

Ga. 

Fla. 

Ga. 

Kv. 

Tenn. 

Miss. 

o. 
o. 

Miss. 

O. 

Md. 

Pa. 

Del. 

N.  J. 

O. 

Pa. 

Ind. 

Tenn. 

III. 

Pa. 

N.  J. 

N.Y. 

N.  Y. 

N.Y. 

Mich. 


— Stofiped  Clocks. 

DUtftnce. 
0 
20 


89 
89 
103 
111 
192 
203 
211 
252 
405 
438 
481 
488 
491 
491 
600 
506 
515 
526 
538 
552 
558 
565 
581 
687 
588 
«)08 
640 
643 
645 
696 
866 


Time, 
61 '"06' 
51    12 
51 

51    56 
53 
52 
52 

51  30 
52 

62  22 
63 

54  12 
66 

55 

64 

64  21 

54 

64  26 

56 

65 

54 

54 

55  46 
55 

55 

54  50 

53 

55 

65 

68 

66  16 

56 

67 


No.  of  clocks. 

4 

2 
2 

1 

1 

2 

1 

1 

4 

I 

1 

1 

1 

3 

1 

1 

4 

1 

1 

1 

1 

1 

1 

i 

6 
1 
1 
1 
1 
2 
1 
1 


wt. 

3 
2 
2 
1 
1 
2 
1 
1 
3 
1 
1 
1 
1 
2 
I 
1 
3 
1 
1 
1 
1 
1 
1 
1 
4 
1 
1 
1 
-     I 
1 
1 
1 


We  may  arrange  these  in  groups  or  sets  according  to  their 
distances,  as  was  done  in  the  discussion  of  group  III,  and  ob- 
tain the  following  equations  of  condition. 

Weight.        BmMiuU. 

0  to  89  a  +  59y  =  15  7  +  1229 

103  to  192  X  +   150y  =69  4  -  7-21 

203  to  262  a  +  234y  =110  5  —  16*37 

405  to  491  »  +  469y  =194  7  -  11-29 

600  to  688  X  +  549y  =  209  16  +  4'04 

608  to  696  X  +  642y  =  237  6  +  12*80 

866  X  -\-  865y  =  364  1  -  24*97 

The  normal  equations  are : 

45a;  +  183336  y  =  7172. 
V  I8886a5  +  9667896  y  =  8717238. 


» 


locki. 


Wt. 

8 

2 

2 

1 

1 

2 

1 

1 

8 

1 

1 

1 

1 

2 

I 

1 

8 

1 

1 

1 

1 

1 

1 

1 

4 

1 

1 

1 

1 

1 

1 

1 


ne  to  their 
II,  and  ob- 


Propagation  of  the  Cka/rle^ton  Earthquake. 


15 


From  which  a?  =  +  5'0,  y  =  0-379.  The  resulting  speed  is 
2 '638  ±  O'lOS  miles,  or  4246  ±  168  meters  per  second.  If  the 
correction  for  the  systematic  error  has  a  value  approximately 
that  which  has  been  derived  from  the  comparisons  of  the 
stopped  clocks  with  well  determined  times  of  particular  locali- 
ties, or  not  less  than  one-fifth  the  amount,  the  corrected  speed 
would  be  from  5100  to  5200  meters. 

We  may  now  proceed  to  combine  the  results  of  the  first  three 
groups  and  obtam  from  them  a  single  mean.  The  probable 
error  of  the  fourth  group  being  uncertain  it  is  necessary  to 
omit  it.  Taking  the  weights  inversely  as  the  squares  of  the 
probable  errors  we  have : 


Group  I, 
Group  II, 
Group  III, 

Mean  result, 


5205"'  ±  168"» 
6192'°  ±  236'° 
5171°' ±  116'° 

6184'»±    SO"" 


wt. 
2 
I 
4 


It  remains  to  inquire  whether  the  data  indicate  any  variation 
of  the  speed.  The  answer  is  in  the  negative.  The  data  are 
inconsistent  with  any  variation  of  a  systematic  character  and 
thera  is  no  apparent  means  of  detecting  an  unsystematic  one. 
A  smdl  irregular  variation,  such  as  mi^ht  be  caused  by  varying 
density  and  elasticity  of  the  propa^ting  medium,  would  not 
be  inconsistent  with  the  data ;  but  nie  evidence  of  it  cannot  be 
separated  fiom  the  errors  of  observation. 


MiuU. 

12-20 
7-21 
16-37 
11-29 
4-04 
12-80 
24*97 


"iHB^K 


■^aeB9m»,M»-fa^' 


tm 


rrr" 


♦•* 


